Container closures frequently incorporate metal discs which have a raw edge by virtue of the stamping process utilized in forming the disc. In conventional twist caps the cut or raw edge is turned under and not exposed directly to any moisture so that no particular problems are presented thereby.
There has recently been developed a closure which consists of a plastic band which is pressed and thumbed or pryed off a glass container. Such closures also include an inner metal insert which affords both product protection and decorative appeal to customer. An ideal material for such metal discs would be a steel disc being, for example, tin plated or chrome plated to provide resistance to corrosion. If such a material, however, were used in the above type closure, its raw edge would be exposed thereby also exposing the steel which is readily susceptible to corrosion. Consequently, although steel has numerous advantages such as magnetic properties for handling both closures and packages, strength, and lower cost, the steel disc has not been used but rather non-corrosive materials such as aluminum have been used to avoid excessive rusting which could occur even if the closure were cold sealed and stored in humid conditions.